Embodiments of the invention relate to an image processor for and a method of performing a tonal transformation on image data.
An image scanned using an imaging device (e.g., a scanner, a multi-functional device such as a scanner-printer-facsimile machine, etc.) may have several tonal transformations performed on it before the resultant image is either displayed (e.g., on a personal computer (PC)) or printed (e.g., via a printer). One common type of tonal transformation is known as gamma correction. Gamma correction is usually performed by applying a power-law transformation to the pixels of a document. The correction maps input intensity values into transformed, output intensity values. The transformation has the basic form ofs=crγ  [e1]where r is the input intensity value, s is the output intensity value, and c and γ are positive constants. Values for γ<1 has the effect of making the output lighter than the input, while values for γ>1 has the effect of making the output darker than the input.